Liquid-level sensor

ABSTRACT

An absorption refrigeration system including generator-solutionlevel sensing means to prevent heat input to the generator unless a predetermined minimum amount of solution is present therein.

United States Patent Inventor Gerald K. Gable North Syracuse, N.Y.

Appl. No, 829,621

Filed June 2,1969

Patented Sept. 7, 1971 Assignec Carrier Corporation Syracuse, N.Y.

LIQUID-LEVEL SENSOR 2 Claims, 2 Drawing Figs.

U.S. Cl 62/148,

, 62/476, 137/392 Int. Cl F251) 15/04 Field of Search 62/ 1 48; 137/392 [56] References Cited UNITED STATES PATENTS 2,385,161 9/1945 Pinkerton 137/392 3,279,204 10/1966 Palmatier 62/148 X 3,367,137 2/1968 Whitlow 62/148 Primary Examiner-William F. ODea Assistant ExaminerP. D. Ferguson AttorneysHarry G. Martin, Jr. and J. Raymond Curtin ABSTRACT: An absorption refrigeration system including generator-solution-leve] sensing means to prevent heat input to the generator unless a predetermined minimum amount of solution is present therein.

PATENTED SEP 7 l97l INV! NTOR GERALD K. GABLE.

ATTORNEY.

LIQUID-LEVEL SENSOR BACKGROUND OF THE INVENTION In absorption refrigeration systems, a number of conditions may be encountered which result in a low solution level in the generator. This condition is especially prevalent at startup or if the pump or solution transfer device malfunctions. Under these conditions, the generator is quickly overheated. Temperature-sensing devices are therefore commonly employed to shut the machine down when the generator overheats. However, if there is a malfunction, the generator must overheat before the machine shuts down which is detrimental to the generator. Further, an operating condition could be encountered which would cause a fairly long delay in providing solution to the generator, causing the generator to overheat and the machine to shut down even though there is no malfunction. The machine would ordinarily then have to be restarted by a Serviceman.

SUMMARY OF THE INVENTION This invention relates to an absorption refrigeration machine having a generator and condenser on the high-pressure side and an absorber and evaporator on the low-pressure side thereof connected to provide refrigeration.

A solution-level sensor, operably associated with the generator heating means, prevents operation of the heating means unless a predetermined minimum quantity of solution is present in the generator.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic diagram of an absorption refrigeration machine; and

FIG. 2 is an enlarged sectional view of a generator-solutionlevel sensing device employed with the refrigeration machine of FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT strong absorbent solution refers to a solution which is strong in absorbent power. A suitable absorbent for use in the system described is water; a suitable refrigerant is ammonia.

Liquid refrigerant condensed in condenser 12 passes through refrigerant liquid passage 24 to the liquid-suction heat exchanger. The liquid-suction heat exchanger 18 includes a housing 26 having a refrigerant restrictor 28 at the upstream end thereof and refrigerant restrictor 30 at the downstream end thereof. A portion of the liquid refrigerant supplied to the liquid-suction heat exchanger 18 flashes upon passing through restrictor 28 due to the low pressure existing downstream of the restrictor, thereby cooling the remainder of the refrigerant in the housing 26. The cooled refrigerant liquid and flashed refrigerant vapor then pass through restrictor 30 into heat exchanger 32 of chiller 14.

A heat exchange medium such as water is passed over the exterior of heat exchanger 32 where it is chilled by giving up heat to evaporate the refrigerant within the heat exchanger. The chilled heat exchange medium passes out of chiller 14 through line 34 to suitable remote heat exchangers (not shown) after which it is returned to the chiller through inlet 36 for rechilling.

The cold refrigerant evaporated in heat exchanger 32, along with a small quantity of absorbent which is carried over to the chiller with the refrigerant from the generator, passes into refrigerant vapor passage 38 of liquid-suction heat exchanger 18. The refrigerant vapor and absorbent liquid, which has a large quantity of refrigerant absorbed therein, passes through refrigerant vapor passage 38 in heat exchange relation with the refrigerant passing through housing 26. REfrigerant vapor passage 38 is provided with a turbulator 40 which consists of a twisted metal strip to provide a tortuous flow path for the vapor to provide optimum heat transfer between the vapor and liquid in passage 38 and the liquid refrigerant in housing 26. By passing the vapor and liquid in passage 38 in heat transfer with the liquid refrigerant in housing 26, a large quantity of refrigerant in the absorbent liquid in passage 38 is vaporized. The heat of vaporization is therefore removed from the liquid refrigerant supplied to heat exchanger 32. This heat transfer within the liquid-suction heat exchanger 18 provides an increase in the absorption machine efficiency by transfer ring heat from the liquid supplied thereto from the condenser to the refrigerantvapor and absorbent liquid discharged from the chiller.

Refrigerant vapor and absorbent solution from passage 38 is supplied to refrigerant distributor 20 through line 42. Strong solution, which is supplied from the generator to distributor 20 through line 52, mixes with the vapor and solution supplied to the distributor through line 42. The refrigerant vapor-absorbent solution mixture from distributor 20 is supplied to individual circuits 58 of the absorber 10 through absorber supply tubes 56. A cooling medium, preferably ambient air, is passed over the surface of the absorber by fan means including motor 59 in heat exchange relation with the solution therein for cooling the absorbent solution to promote the absorption of the refrigerant vapor by the solution. The same cooling medium may be supplied to condenser 12 in heat exchange relation with refrigerator vapor therein to condense the refrigerant.

Cold weak absorbent solution passes from absorber 10 through line 61 into pump 22. Liquid from pump 22 is passed through line 63 to rectifier heat exchange coil 64. The weak solution passes through coil 64 in heat exchange relation with hot strong solution passing through heat exchange coil 66 disposed within coil 64 and with the hot refrigerant vapor flowing through rectifier shell 68 in contact with the outer surface of coil 64. The weak solution from coil 64 is discharged into the upper portion of generator 16 along with any vapor which is formed in coil 64 due to heat exchange with the hot vapor passing thereover and the hot solution flowing therethrough.

Generator 16 comprises a shell 70 having tapered fins 72 suitably affixed thereto as by welding. The generator is heated by a suitable heating means, such as a gas burner 73 having an electrically actuated valve 74 associated therewith to control the flow of gas to the burner. An electrical circuit including a room thermostat 77, relay 83, transformer 85, gas valve 74, level sensor 75, pump motor 19, and fan motor 59 is provided to control the machine. When the thermostat 77 closes in response to room temperature, the circuit including relay 83, valve 74, and sensor is completed. The relay 83 in turn completes the circuit including fan motor 59 and pump motor 19. It can be seen by reference to FIG. 1 that the relay 83 is connected in parallel with gas valve 74 and sensor 75. In the event there is an insufficient quantity of solution in the generator, the portion of the circuit including sensor 75 and gas valve 74 will remain open. The gas valve will therefore remain closed and no heat will be provided to the generator. However, relay 83 will be held closed. The pump 19 will therefore remain in operation for forwarding solution to the generator. When a sufficient quantity of solution has been provided to the generator, the circuit through sensor 75 and gas valve 74 will be completed. The gas valve 74 will open and heat will be supplied to the generator. Should the solution level in the generator drop during any time or during any period of machine operation, the gas value will temporarily close until the solution reaches the proper level.

Referring more particularly to FIG. 2, the level sensor 75 comprises a threaded plug 81 having an electrically conductive probe 79 and an insulator 84 projecting therethrough and sealed thereto by suitable means such as brazing. The level of absorbent solution in the generator fluctuates to some extent under normal operating conditions. The probe is therefore located within the generator so as to be below the lowest normal solution level in the generator but high enough to sense the drop of solution below the normal level to immediately interrupt the heat input to the generator. If there is a sufficient quantity of solution in the generator so that the probe 79 of sensor 75 is submerged in solution, the gas valve portion of the control circuit will be completed, thereby permitting gas to flow to the burner 73 to heat the solution in the generator. If there is an insufficient quantity of solution in the generator, the gas valve circuit will not be completed through the sensor 75 until pump 22 has provided enough solution to the generator to submerge the probe.

Since the generator will remain within safe operating temperatu're limitations as long as there is sufficient solution to cover probe 79 of sensor 75, the danger of overheating the generator is remote. Should another portion of the system such as the solution pump fail, the machine will shut down almost immediately due to the rapid drop of solution in the generator below the level of sensor 75.

The above-described control system is far superior to a control system employing high temperature limit switches to shut off the machine when the generator overheats. These switches actually require the generator to be overheated before the machine will shut down. By utilizing a solution sensor in the generator to control heat input thereto, a problem is sensed before generator temperatures can rise, and detrimental overheating of the generator is avoided.

A second, seemingly unrelated advantage in machine operation is obtained by utilizing the solution-level sensor to control the heat input to the generator. As ambient temperature drops, it is sometimes difficult to start aqua-ammonia absorption refrigeration machines as the solution level in the generator initially rises, causing solution to pass into the condenser. This reduces the already low, high side pressure-and causes violent boiling in the generator. The solution level in the generator will then drop to a point where the generator overheats and the machine shuts OH in response to the thermal sensor normally employed in an absorption refrigeration machine. Once the machine is shut off by the thermal sensor, it may be necessary to manually reset the controls to place the machine back in operation.

With the solution sensor, if the level in the generator drops shortly after startup, the burner would shut off, the level in the generator would again rise, and the burner would turn on again. The machine can cycle ON and OFF under these conditions until the temperature, of the machine reaches a high enough level to allow proper operation of the machine.

The weak solution in generator 16 is boiled to form a strong solution and refrigerant vapor. The hot strong absorbent solution passes upwardly through the analyzer section of generator 16 through analyzer coil 76 in heat exchange with the weak solution passing downwardly over the coil. The wann strong solution then passes through heat exchange coil 66 within coil 64 and line 52into the distributor 20. A restrictor 78 is provided in line 52 so that the solution supplied to the vapor distributor 20 is at the same pressure as the vapor in line 42.

Refrigerant vapor formed in generator 16 passes upwardly through the analyzer section thereof where it is concentrated by heat and mass .transfer with weak solution passing downwardly over analyzer coil 76. Analyzer plates 80 in generator 16 provide a tortuous path for flow of solution and vapor to assure intimate contact therebetween to improve the mass heat transfer. The vapor then passes through rectifier 68 in heat exchange relation with the weak solution passing through coil 64. Absorbent condensed in rectifier 68 flows downwardly into the generator along with the weak solution discharged from coil 64. Refrigerant vaporzpasses from rectifier 68 t rough line 82 to condenser l to complete the refrigeration cycle.

lclaim:

1. An absorption refrigeration machine having a generator, condenser, evaporator and absorber connected to provide refrigeration,

a solution pump adapted to pump absorbent solution from said absorber to said generator,

fan means associated with said condenser and said absorber for passing air in heat exchange relation therewith to cool the absorbent solution and refrigerant therein,

heating means adapted to heat the solution in said generator, said heating means including a gas burner,

a gas valve adapted to control the supply of gas to said burner, solution-sensing means associated with said generator and said heating means to prevent said gas valve from opening if a predetermined minimum quantity of solution is not present in said generator, said solution-sensing means being disposed within said generator at a location below the lowest normal generator solution level while being high enough to sense a drop of solution below the normal level to immediately close said gas valve; and

temperature-responsive means disposed in the area served by said absorption refrigeration machine to actuate said machine upon a rise in temperature of the area, said temperature-responsive means actuating said solution pump and said fan means irrespective of the solution level in said generator to supply sufficient solution to said generator to allow said gas valve to open, said sensing means cycling said gas valve open and closed upon startup until the quantity of solution supplied to said generator is at least equal to the quantity of solution boiled from sald generator to allow uninterrupted operation of said heating means.

2. An absorption refrigeration machine according to claim 1 wherein said solution-sensing means includes a plug adapted for attachment to the wall of said generator,

electrically conductive probe means projecting through said plug into the interior of the generator, and

an insulator disposed within said plug and sealed thereto to insulate said probe from said plug, said probe being sealed to said insulator to prevent leakage of absorbent solution from the generator through said solution sensing means.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. lOLL Dated September 7, 1971 Inventor GERALD K GABLE It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 2, line 1 L, after liquid, it should read --in housing 26, thereby reducing the temperature of the liquid-- Column 2, line 3 4, "refrigerator should read --refrigerant-- Column 2, line 7 L, value" should read -valve Signed and sealed this 1 8th day of July 1972.

(SEAL) Attest:

EDWARD M.FLETCHER,JR. ROBERT GOTTSCHALK Attesting Officer Commissionerof Patents RM PO-105O (10-69) USCOMM-DC 60376-969 h u s GGVERNMENT PRINTING orncz: I959 o-ass-Ju 

1. An absorption refrigeration machine having a generator, condenser, evaporator and absorber connected to provide refrigeration, a solution pump adapted to pump absorbent solution from said absorber to said generator, fan means associated with said condenser and said absorber for passing air in heat exchange relation therewith to cool the absorbent solution and refrigerant therein, heating means adapted to heat the solution in said generator, said heating means including a gas burner, a gas valve adapted to control the supply of gas to said burner, solution-sensing means associated with said generator and said heating means to prevent said gas valve from opening if a predetermined minimum quantity of solution is not present in said generator, said solution-sensing means being disposed within said generator at a location below the lowest normal generator solution level while being high enough to sense a drop of solution below the normal level to immediately close said gas valve; and temperature-responsive means disposed in the area served by said absorption refrigeration machine to actuate said machine upon a rise in temperature of the area, said temperature-responsive means actuating said solution pump and said fan means irrespective of the solution level in said generator to supply sufficient solution to said generator to allow said gas valve to open, said sensing means cycling said gas valve open and closed upon startup until the quantity of solution supplied to said generator is at least equal to the quantity of solution boiled from saId generator to allow uninterrupted operation of said heating means.
 2. An absorption refrigeration machine according to claim 1 wherein said solution-sensing means includes a plug adapted for attachment to the wall of said generator, electrically conductive probe means projecting through said plug into the interior of the generator, and an insulator disposed within said plug and sealed thereto to insulate said probe from said plug, said probe being sealed to said insulator to prevent leakage of absorbent solution from the generator through said solution sensing means. 